Charged-particle beam transport systems often include magnetic elements for partial beam focusing. These systems often require that the magnetic elements be aligned so that the axis of their magnetic field lies on a beam axis of the transport system. Intuitively this may be accomplished by aligning the mechanical axis of the magnetic elements with the beam axis, but it may be the case that the magnetic and mechanical axes of the magnetic element are not aligned. Techniques have therefore been developed for determining the magnetic-field axis of a magnetic element so that it may be aligned with the beam axis in an appropriate charged-particle beam transport system.
A widely used existing technique for determining the magnetic-field axis of a magnetic element involves sending a current pulse along a wire stretched along the putative axis while the magnetic element is energized, and monitoring the wire for any resulting deflection. This method, however, involves the generation of high-voltage pulses, often requires close inspection of the wire and has a limited rate at which observations may be performed. A second technique uses a swept frequency alternating current in the wire, whose motion in numerous (on the order of 30) harmonic vibrational modes may be detected using a phototransistor. The spatial distribution of the transverse magnetic field may then be reconstructed numerically using the data from the harmonics. This second technique, however, requires many minutes to make the required frequency scans.
Therefore, it may be desirable to have a system and associated method of determining the magnetic-field axis of a magnetic element that takes into account at least some of the issues discussed above, as well as possibly other issues.